Large-scale integrated circuits (LSIs) have higher and higher integration densities and are produced at higher and higher speeds in the field of photolithography, which is a fine patterning (microfabrication) technology. Accordingly, resist materials that can provide for the higher integration and higher speed production have been intensively developed. Such resist materials recently mainly require nano-level control of surface smoothness after development and good sensitivity even upon the use of low-power light sources. Resist materials having both of these properties are excellent in resolution, line width roughness (LWR), and sensitivity and are possibly usable typically as resist materials that are used for extreme-ultraviolet radiation (EUV) and enable extremely highly fine patterning.
Exemplary proposed resist materials are resins each including a polymer backbone having carboxy or phenolic hydroxy in side chains, and containing an acid-degradable substituent introduced into the polymer backbone (see Patent Literature (PTL) 1 and PTL 2). The resin disclosed in PTL 1 employs a t-butyl ester group as the acid-degradable substituent. In contrast, the resin disclosed in PTL 2 employs an acetal group as the acid-degradable substituent.